This invention was made with Government support under Grant Contract No. DE-FG 03-87-ER 13752 awarded by the DOE. The Government has certain rights in this invention.
This invention relates to a method of accelerating photons in a plasma and more particularly to a method of upshifting the frequency of a pulse of laser light by propagating it along a relativistic plasma wave.
It has been proposed and demonstrated by computer simulation that a pulse of intense laser light can be used to generate an intense plasma wave with phase velocity close to that of light (See "Laser Electron Accelerator" by T. Tajima and J. M. Dawson in Phys. Rev. Lett. 43, 267 (1979)). A wake of plasma oscillations is created by such an intense electromagnetic pulse through the action of the nonlinear ponderomotive force and electrons trapped in the wake can be accelerated. As such an intense plasma wave is used to accelerate electrons, the frequency of the light is degraded in the process.
In view of the above, the present inventors considered the feasibility of upshifting the frequency of light, or accelerating photons, by reversing the process described above, that is, by propagating photons along an intense plasma wave. It has been demonstrated that such an intense plasma wave can be generated by a beat-wave accelerator (as disclosed, for example, by T. Tajima and J. M. Dawson, ibid.) or a plasma wake-field accelerator (as disclosed, for example, in "Acceleration of Electrons by the Interaction of a Bunched Electron Beam with a Plasma" by P. Chen, J. M. Dawson, R. W. Huff and T. Katsouleas in Phys. Rev. Lett. 54, 693 (1985)).